Compressor, vacuum-pump, and the like.



F. J. ROUHOWL comrimsson, VACUUM PUMP, AND THE LIKE.

' {APPLICATION FILED MAY 31', 1006.

Patented May 11, 1909.

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F. JJROGHOW. COMPRESSOR, VACUUM PUMP, AND THE LIKE.

APPLICATION FILED MAY 31, 1906.

Patented May 11, 1909. Fire 2 v 3 SHEETS-SHEET 2.

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F. J; ROGHOW.

commmsson, VACUUM PUMP, AND THE LIKE.

APPLICATION FILED MAY 31, 1906.

Patented May 11, 1909.

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WITNESSES:

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FERDINAND J. ROOHOW, OF BROOKLYN, NEW YORK.

COMPRESSOR, VACUUM-PUMP, AND THE LIKE.

Specificationof Letters Patent.

Patented May 11, 1909.

Application filed. May 31, 1906. Serial No. 319,454.

- To all whom it may concern:

Beit known that I, FERDINAND J. RooHow, of Brooklyn, in the county of Kings, New York, have invented certain Improvements in Compressors, Vacuum-Pumps, and the Like, of which the following description, in connection with the accompanying drawings, is a specification, like characters on the drawings designatin like parts. v

This invention relates to compressors of air or other gases, including so-called vacuurn-pumps, and especially to such forms of the same as are operated by a reciprocating piston.

The object of my invention is first to neutralize, practically completely, in the aforesaid type of compressors and vacuum-pumps, the loss of efficiency caused by the compressed gases remaining on the suction side in clearance spaces between the piston and cylinder head and in those of. inlet and outlet channels of suction anddelivery valves, when the piston has reached either end of its stroke. In existing apparatus of this type, these compressed gases, when thus confined, expand as the piston commences its return movement and prevent the opening of the suction valves until the pressure of the expanding gases is as low, or a trifle lower, than that in suction side; until then the piston can do no work; it is only from the moment that suction commences that action of the piston commences. That part of. the stroke of the piston thus traversed is a total loss to the theoretical efficiency of the piston, as the.

latter is afunction of the total stroke of same.

A second object of my invention is to increase the efiiciency on the compression side, by transferring from the suction to the compression side, the bulk of these confined gases. v

The nature of my invention residesfirst in providing a separate passage between the two ferred from these clearance spaces to the op-' posits side of the piston' It is evident from the above'description that the aforesaid passage may be located either within the piston or outside of same, within or connected with the cylinder.

valves and 9 the discharge valves.

in cylinder.

My invention is of such general utility that it is not to be understood as confined to one special constructlon or device described, as

reciprocating piston type.

The following specification and its accompanying drawings, forming a part of same, describe my invention as applied to a simple type of compressor and will make the character of my invention, its operation and one convenient form of construction, perfectly clear to the mechanic skilled in. the art, and will not only enable him to reproduce the device on similar types of compressors, but will make easily apparent to him how to apply the invention to any other type, as the invention is so simple that it is only a matter of ordinary engineering routine to apply it to any style or construction of a reciprocating piston compressor.

7 In the drawings, Figure 1 is a vertical section through the center line A'B of a cylinder belonging to a compressor or vacuum pump; Fig.2 is a top view of the cylinder head of same taken from line CD Fig. 3 is a cross section through the cylinder by the line EF; Figs. 4 and 5 a front view and sectional side elevation of the general arrangement of a complete compressor or vacuum pump; Figs. 6 and 7 are detail views of the housingof suction valves; Fig. 8 is a detail view of cam for operating suction valves and Fig. 9a detail view of cam for operating equalizing valves.

In the embodiment of my invention selected for illustration and description as a convenient form to enable ready and complete understanding of my invention, the part designated by the reference numeral 1 is the cylinder of a gas orair compressor 2 its piston; 3 its piston-rod; 4 the cylinder head; 5 the cylinder bottom; 6 a channel for the discharge of the compressed gases, and 7 (see Figs. 2, 3, 4 and 5) a channel for the suction of the gases. 8 designates suction These constitute the necessaryparts of an ordinary compressor, while my improvement consists principally in a channel 10, establishing a directcommunication between the two ends it is easily applicable to any apparatus of a of the cylinder 1, preferably without any other inlet or outlet, and valves 11 which are located one at each end of this channel, preferably opposite the suction valves so as not materially to increase the clearance space of'the channel 12 (see Fig. 1). The valves 11 are positively opened and shut by means of levers 13, spiral springs 14 and earns 15 (see Figs. 3, 4 and 5), in such a way that each one opens and shuts during a very short period of the rotation of the crankshaft 24 and at a moment when the piston passes either end of its stroke. The levers 13 are supplied at their outer ends with steel rollers 16 rolling along the periphery of cams 15. The suction valves 8 are similarly and positively operated by means of levers 18, springs 19 and earns 17, which latter are shaped and adjusted in such a way that the valve 8 on the piston side commences to open a trifle after the valves 11 have shut and that valve 8 away from piston shuts a trifle before valves 11 have opened. The discharge valves 9 are ordinarily used automatically working cheek-valves, with stems guided in covers 21, and spiral springs 22 to seat them automatically. Figs. 4 and 5 show the general arrangement for the operation of the positively driven valves.

The parts designated by the reference numeral 23 are two A frames supporting the compressor cylinder below and the crank shaft above, with guides in middle for crossheads 25. The bottom cylinder head 5 is bolted by means of two cross beams 26 to frames 23 while the tops of these frames form pillow blocks 27 in which crank shaft 24 revolves. On that end of the crank shaft nearest to the suction and equalizing valves is fastened firmly a spiral gear 28 which meshes into another spiral gear of the same number of teeth 29 and which is fastened permanently to the top of an auxiliary shaft 30, so that both these shafts make exactly the same number of revolutions, and the frame 23 is furnished with three bearings 31, guiding the shaft 30, and lastly the four disk-cams 15 and 17 are fastened to said shaft and adjusted properly opposite levers 13 and 18 so that the opening and closing of valves 8 and 11 is done in the required relation to the position of the crank in every revolution of the crank shaft.

From the above description we can easily trace the operation of the device as follows: As the piston travels one way or the other there is always suction of gases behind it, the suction valves being open almost during the whole stroke, and compression in front of it, the discharge valves opening automatic ally to allow escape of the gas under compression. When the piston has almost reached the end of its stroke, the suction valves are positively closed and immediately after this i. e. immediately prior to or after commencement of the suction stroke, when all posible compression shall have been accomplished, the equalizing valves are opened and the compressed gas in front of the piston will rush immediately through channel 10 into the other side of the cylind er (whereby the discharge valve of the piston side will also instantly close) until the pressure of gases will he equalized within the cylinder, on both sides of the piston. This equalization. will be obtained very quickly and the equalizing valves must only be opened a very short time as they ought to be shut when equalization has occurred. As the space in front of piston is only very small at the moment when equalizing valves open, the equalized pressure in front and behind piston will be only slightly above the pressure on the suction side when the equalizing valves close, and a slight motion. of the piston after reversal will sul'lice to create a suflicient vacuum on that side of the piston which is now retiring from the cylinder head, to allow suction through suction valve, which latter is opening at this stage of the travel of the piston. Thus it is seen that the suction will last almost during the whole stroke of the piston and that the loss of efliciency by reason of clearance spaces at end of stroke of piston as far as suction is regard ed is insignificant. Afterequalization about of the quantity of the compressed air which was confined before it in clearance spaces has been transferred to the opposite or compression side of the piston and thereby the capacity of the compressor increased to a certain extent. ln order to exemplify the insignificance of said respective loss and the amount of said respective gain in capacity, and to facilitate comparison between this improved compressor and the ordinary style, we will assume that the capacity of the cylinder, meaning the prodnet of area and stroke of piston, may be named Z, the sum of clearance spaces on either end of cylinder X, the pressure on the compression side of piston p and the pressure on suction side of same c. When piston arrives at either end of its stroke, the gases within cylinder will be distributed as follows :Tn front of piston will be a space a: 1

filled with gas at a pressure P, and behind the piston will he a space 1 plus a; filled with gas, at a pressure 4;. The equalizing valves 11 open and shut now in quick succession, allowing only time enough when. open to obtain equalization of pressure on both sides of cylinder; thus the air confined in a; with pressure p expands now into a total space of 1 plus 250, therefore its pressure will be reduced to 1 1 plus 200 and the air confined in space 1 plus :25, with a pressure of v, expands li (GWlSG into the total ames space 1 plus 201; and will attain after expane sion a pressure of i (1 pl s 2012 1 plus 291;

The sum of both the pressures is the total equalization pressure, equals :20 times p (1 plus @12- r 200 P us equals :rp plus (1 plus w) 'v A few numerical examples will now clearly establish the reat advantage of my invention, compared with the usual type.

First example:

Let 12 equal 1 (atmosphere) u u a 0.02

equals 1.07 atmospheres.

The amount of clearance spaces is 0.02; when this is increased to 0.02 X 1.07 the pressure will be reduced to 1 atmosphere and the action of the piston on suction side will commence then, 0.02 X 1.07 equals-0.0214; if therefore iston has traveled only 0.0214 0.02, equa s 0.0014 of its stroke, suction will commence and the efliciency of the work of piston on the'suction side will be 1 40.0014, e uals 0.9986; the pressure on compression si de has increased. by equalization from 1 to 1.07 atmosphere. Therefore the gain on this side is 0.07 and deduct from this the aforesaid loss of 0.0014 gives a total gain of 0.07 0.0014, equals 0.0686, or a gain of almost 7% beyond the theoretical efficiency of 1. TV here there is no equalization, howeventhe gases in clearance spaces 0.02 have to expand 5 times before atmospheric pressure is reached and suction commences, that is, 5 X 0.02 equals 0.1 and therefore 0.1 -0.02 is the travel of piston required until then, so that 8% of the total eiiiciency is lost in this case. The com arison shows therefore in this case a total oss of 8% and on the former case a gain of 6.8% or a total diflerence in favor of equalization of 14.8%.

Second example:

Let 22 equal 1 (atmosphere) 2) K 5 If 9c 0.04;

The pressure after equalization by substitution will be 5 times. 0.04 plus 1.04

or 1.148: atmosphere, and this multiplied by the amount of clearance spaces 0.04, and less clearance space, will leave amount of travel of piston before suction commences; 'i. 6., 1.148 X 0.04 0.04 equals 0.148 X 0.04 equals 0.00592, or slightly over a of one per cent. of the travel of stroke is here lost on theoretical efficiency on the suction side of piston, while the actual gain on compression side after equalization is 1.148 1 equals 0.148, therefore here total gain again equals 0.148 0.00592 equals 0.14208, while the loss without equalization is (5 1)0.4 equals 0.16. Thus the comparison in this example is as 16 plus 14.2 equals 30.2 per cent. in favor of the equalization system. This example shows that the amount of clearance space affects the efficiency of this invention only very slightly, while when equalization is not used the suction Will commence when the piston has traveled (5 1)0.04 equals 0.16, or 16% of its stroke. The losses in this case compare therefore as 0.00592 to 0.16, or as 1 to 27 in favor of my im rovement.

Third examp e:

Let 0 equal 1 (atmosphere) p H l I a: 0.04

Here the pressure after equalization is 26 times 0.04 plus 1.04

equals 1.92 atmosphere,

andthe travel of piston before suction commences equals (1.92 1)0.04 equals 0.0368 or only3 and 5; per cent. of the theoretical efiiciency is here lost on suction side while the gain in quantity on compression side is 1 1.92 atmos here equals 0.92 atmosphere, and the su traction of loss from gain equals 0.92 0.0368 leaving a total gain by equalization of 0.8832, while in an ordinary compressor, without equalization, the pressure on suction side of piston will reach the pressure of the atmosphere when it arrives at the end of its stroke, namely 26 times 0.04 -m equals 1,

and the compressor will not be able to do any making a direct passage within the piston from one side of it to the other, instead of within the cylinder and by devising mechanism for positively operating equalizing valves to control communication through such passage, but it is so important in all mechanism operating valves to provide for the greatest possible facility for taking out valves for inspection or repairing and also for the quick and reliable readjustment of their motion, that I prefer to describe a device comprising a passage outside of cylinder, and valves and valve-motion which are under constant supervision and if necessary can be taken apart quickly.

The general practice now adopted in compressing to a high pressure is compounding a number of compressors, one compressing into the other one, in order to diminish their enormous loss of efliciency as much as possible, but with the adoption of my simple device of the passage and two valves, a single cylinder is sufflcient to compress to the highest pressure in practical use, not only without loss of efficiency but with a considerable gain of same on account of filling the whole cylinder of a compressor by equalization at end of stroke of piston, with a higher pressure than the atmospheric pressure and therefore increasing its natural capacity. For instance if the compression is assumed to be 100 atmospheres and the clearance s ace in each end of cylinder to be 0.015 then the equalization pressure will be The travel of the piston from the end of its stroke until suction commences will there-- fore be (2.4 1 )0.015 or 0.02 or 2 per cent. of its whole travel, so that there is only a loss of 2 per cent of the theoretical eiiiciency on the suction side, compressing in a sin le cylinder from 15 pounds ('6. e. atmospheric pressure) on the one side to 1500 pounds of pressure on the other side. The gain 011 compression side is 2.4 1 equals 1.4 atmosphere, hence total gain equals 1.4 0.02 equals 1.88, so that the capacity of a compressor of my improved system under these conditions would be actually 138 per cent.

' larger than a theoretically correct compressor without this system could attain, showing an efficiency of 2.38. A single cylinder compressor of the ordinary reciprocating style however could not attain any suction whatever and therefore could do no work whatever, under the conditions just de scribed.

As a so called. vacuum pump is nothing else but a compressor of gases, compressing them from a very rarefied state into the atmosphere, and as the accompanying drawings represent not only the arrangement able with such clearance space.

most preferable for a compressor, but also, without any change in any of its details, for a vacuum pump, it remains to show the advantage of this invention when the pump is intended for that purpose. o have here a compressor which shall compress on one side to 15 lbs. (or atmospheric pressure) to the square inch, and on the other side it shall reduce the inhaled gases to the lowest possible pressure, but the lowest possible pres sure on suction side is evidently reached when the piston is unable to discharge any more gas at atmospheric pressure, it being only able to fill clearance spaces with atmospheric pressure, because as there is then no discharge, neither can there he suction any longer. if we now assume the clearance spaces to be 0.01, and again the capacity oi piston travel to be 1, we can reason as follows: In order that the piston be able to just till 0.01 of the cylinder with a pressure of 15 lbs. and no more, the pressure at commencement oi stroke, but after equalization, must have been 0.15 lbs. While this is 'compressed on one side oi" the traveling piston and "linally lills at end of stroke the clearance spaces with gases of 15 lbs. pressure, a rarefaction of gases occurs on its other side which finally, at the end of its stroke, must or 0.0015 lbs., 0.15 lbs. being 7. amount to 100 the equalization. pressure when suction starts, and this is the lowest pressure attain- As these light pressures are generally measured by the mercury gage and 2 of the same is equal to a pressure of 1 lb. we have on the suctionv side a pressure as low as 0.003 inches, corresponding to a vacuum of 29.007 inches. ll we compare this result in a vacuum pump in a manner analogous to the comparisons we made before with compressors, we lind that in a vacuum pump without equalization and under otherwise the same conditions, (viz, clearance space to be also 0.01 and compression to be just sul'licient to fill this clearance space with gases of 15 lbs. pressure), the greatest rarefaction attainable will be .15 lbs, or 0.3 inches mercury, or just 100 times more pressure remaining than in the case or the vacuum which we can obtain with the same pump by applying my system of equalization. The result in applying this system on vacuum pumps is therefore the same as that obtained in a compressor, namely that by its application we can attainv practically any amount of vacuum with only one cylinder, while the compounding of a number 01 cylinders for this purpose, or a vacuum pump, is even more necessary than on a compressor, when used without my equalizing system.

Although I have described my invention as preferably using puppet valves and a certain style and operation of cams, I do not coniine my invention to these special devices as I may under certain conditions prefer to use slide valves, or reciprocating Corliss valves, or rotary valves, and as I may prefer under such conditions to arrange the cam motion differently to conform better to circumstances, I do not limit myself to the specific illustrated construction of any such details, nor in eneral otherwise than as set forth in my 0 aims, read in connection with this specification.

What I claim and desire to secure by Letters Patent is 1. The combination with a cylinder and its reciprocating piston, of a passage, channel, or chamber in communication with the two sides of said cylinder, to transfer the residual compressed fluid from the clearance to the other end of said cylinder immediately prior to or after commencement of the suction stroke of said piston, and means actuated positively thereupon to prevent retransference of fluid through said passage, substantially as described.

2. The combination with a cylinder and a reciprocating piston therein, of a chamber, channel or passage, forming at times solely a communication between the two sides of said iston, to transfer residual compressed fluid rom the clearance; valves for said passage to control said communication; and means to operate said valves; said instrumentalities cooperating to insure initiation of eflective suction co-incident with the commencement of the suction stroke of said piston, substantially as described.

3. In combination with a cylinder, a reciprocating piston therein, a channel forming at times only a communication between both ends of said cylinder, valves for controlling said communication, to permit transference, immediately prior to or after commencement of the suction stroke, of com ressed fluid to cause decreased pressure on t 1e suction side, and increased pressure on the compression side, during said suction stroke, and positively driven suction valves which are timed to open and shut in. proper conjunction with the operation of said controlling or equalizing valves, so as to insureinitiation of suction. immediately after completion of said equalization, and upon commencement of the suction stroke of said piston, substantially as described.

4. The combination with a cylinder, a reciprocating piston therein and its crank shaft, of a channel forming at times only a communication between both ends of said cylinder, and valves for controlling said communication, including a plurality of positively driven valves, an auxiliary shaft driven from the crank shaft by means of two gear wheels of an equal number of teeth, and

cams actuated by said auxiliary shaft for the operation of all said positively driven valves.

5. The combination with a cylinder, and a reciprocating piston therein, of a channel forming only a communication between both ends of said cylinder to transfer compressed fluid from one end of said cylinder to the other, for the purpose set forth, valves located at the ends of said channel for controlling said communication, and suction valves located opposite said controlling or equalizing valves said valves being res ectively directly adjacent the clearance 0 said cylinder, and having a common communication thereinto.

6. In combination with a cylinder, a reciprocating piston therein, a channel forming only a communication between both ends of said cylinder, to transfer compressed fluid from one end of said cylinder to the other for the purpose set forth, valves for controlling said communication; the auxiliary shaft 30; cams 17 on same; suction valves 8; levers 18 and s rings 19.

7. n communication with a cylinder, a reciprocating piston therein, the channel 10 to transfer compressed fluid from one end of said cylinder to the other for the purpose set forth; valves 11.; spiral springs 14 and levers 13 with an auxiliary shaft 30; gear wheels 28 and 29 and cams 15.

8. The combination with a cylinder and its reciprocating piston of a continuous passage, channel or chamber, forming a communication between the two ends of said cylinder, and means to transfer the residual, compressed fluid from the clearance spaces of one end of said cylinder to the other end of same immediately prior to or after the initiation of a new suction of said piston, and means to prevent a retransfer-ence of any fluid during the remainder of the stroke, substantially as described.

9. The combination with a cylinder and a reciprocating piston therein, of a chamber, channel or passage, forming at times solely a communication between the two sides of said piston, to transfer residual compressed fluid from the clearance spaces, valves for said passage to control said communication, and means to operate said valves; said instrumentalities cooperating to insure initiation of effective suction as well as most effective capacity in compressing, all co-incident with the commencement of the suction stroke of said piston, substantially as described.

Signed at New York city in the county of New York and State of New York this 26th day of May A. D. 1906.

FERDINAND J. ROCHOW.

Witnesses:

ALEXANDER C. PROUDFIT, S. H. GOODAORE. 

